Humans are mammals (哺乳动物). Most mammals are born able to do many things. Some can walk within a few minutes of being born. They have to be able to run away if _________ is near. But human babies are born _________. They need the care of adults to live.

In the first month of life, babies cannot smile or sit up. They cannot even hold up their own heads _________some help from grown-ups.

In the next few months, babies grow a lot. They learn to roll over, support their heads, and _________ sit up while being held.

Babies also have to learn to use their _________. It takes months for them to learn to reach for objects. At around six months old many babies can _________ an object from one hand to another.

Babbling is _________ a human baby learns to speak. Babies all seem to make similar sounds by babbling. They try to imitate (模仿) the sounds they hear from adults. It will take about nine months _________ a baby can say real words.

Somewhere around a baby’s first birthday he or she may stand or walk with help. Soon the baby will _________ around on his or her own!

The first year of a baby’s life is a time of growing and __________. Growing sure takes a lot of work!